The paper making process in paper industry usually comprises pulping, papermaking, and coating. Most types of plant fibers in the raw materials for pulping contain hydroxyl radical, which tend to absorb a large number of tiny foams that are difficult to remove with conventional antifoaming agents on their surfaces and in them; especially, since higher requirements for the quality of paper are put forth today and the operating speed of the paper machine improves continually, a variety of macromolecule additives have to be added in order to improve the quality of products; however, the use of these additives makes the foams produced during agitation and absorbed to fine fibers more stable. If these foams are not eliminated, the paper quality will be degraded, and paper breaking may occur in the paper machine, causing reduced yield and adverse effect on the benefits of the producer. In addition, antifoaming agents are helpful for fiber retaining and filtering, and thereby can reduce fiber loss and avoid water waste, and improve the recovery rate of pulp, attaining considerable economic benefits. Therefore, it is especially important to use antifoaming agents in the paper making procedure.
Existing high-performance antifoaming agents for paper marking are usually fatty alcohol antifoaming agents, with fatty alcohol as the main active ingredient. These antifoaming agents can form oil-in-water emulsion by means of an emulsification process. For example, U.S. Pat. No. 5,807,502 describes an emulsion antifoaming agent constituted by C10˜C28 fatty alcohols, anionic surfactant, and addition product of oxirane and C6˜C18 fatty alcohols, and the viscosity of emulsion prepared by the method described in this document will increase as time goes on; U.S. Pat. No. 4,009,119 discloses an aqueous antifoaming agent composed of long carbon-chain fatty alcohols, fatty acids, dihydric alcohol esters or trihydric alcohol esters of fatty acids, and liquid paraffin; U.S. Pat. No. 4,664,844 discloses an antifoaming agent constituted of C12˜C26 fatty alcohols, C12˜C22 fatty acids, and esters of C12˜C18 monohydric to trihydric alcohols, and hydrocarbons with boiling point higher than 200° C. or C12˜C22 fatty acids, wherein, the involved emulsifying agents include amides, alkyl phenols and fatty alcohol polyoxyethylene ethers, and the viscosity is adjusted through a homopolymer or copolymer of acrylic acid and methacrylic acid to keep the antifoaming agent stable; U.S. Pat. No. 4,950,420 discloses an antifoaming agent for paper industry, which contains 10˜90% of surface active polyethers, such as polyalkoxylated glycerol or polyalkoxylated sorbitol, and 10˜90% of fatty acid esters of polyhydric alcohols, such as monoester and diester of glycol or polypropylene glycol; DE3001387 describes an oil-in-water aqueous emulsion, which is constituted of fatty alcohols with relatively high melting point and hydrocarbons that are in liquid state at room temperature, and the oil phase component can comprise non-aromatic hydrocarbons fatty acids or fatty esters, bee wax, carnauba wax, Japan wax, and Montan wax with relatively high melting point; EP0531713 describes an oil-in-water antifoaming agent, with the oil phase component comprising esters condensed from fatty alcohols with at least 12 carbon atoms, alcohols with at least 22 carbon atoms, and fatty acids with 1˜36 carbon atoms, or esters condensed from fatty alcohols with 12˜22 carbon atoms and monohydric to trihydric fatty acids with 1˜18 carbon atoms, or hydrocarbons with boiling point higher than 200° C., or esters condensed from fatty acids with 12˜22 carbon atoms and polyglycerol, and such emulsion has to be prepared with water soluble emulsifying agents; EP0732134 discloses an oil-in-water emulsion antifoaming agent applied in bubbly aqueous media, with the oil phase component comprising distillation residue of at least a type of higher alcohol that contains more than 12 carbon atoms and is prepared through an oxo-synthesis or Ziegler process, and esters condensed at least 1:1 in mol ratio from sugar alcohol with at least 4 hydroxyl radicals or at least 2 hydroxyl radicals and an intramolecular ether bond and fatty acids with at least 20 carbon atoms, wherein, the residual hydroxyl radicals in the esters can be esterified partially or wholly by fatty acids with 12˜18 carbon atoms, and the oil phase component of the antifoaming agent can further comprise esters condensed from alcohols with at least 22 carbon atoms and fatty acids with 1˜36 carbon atoms, polyethylene wax, natural wax, and hydrocarbons with boiling point higher than 200° C. or fatty acids with 12˜22 carbon atoms.
It is known from existing patent documents and the information of commercial antifoaming agents that fatty alcohol emulsion antifoaming agents inevitably have problems related with storage stability, i.e., the viscosity of emulsion will increase gradually as the time goes; especially, at low temperature, the emulsion may even turn to solid, therefore loses its liquidity in application. Through numerous tests, the inventor introduces fatty acid esters into the antifoaming agent emulsion system, and adds an anionic surfactant in the late stage of emulsification process, so that the anionic surfactant is absorbed on the surface of fatty alcohol and to make the fatty alcohol emulsion more stable under the action of ionic mutual repulsion.